The invention concerns a clutch having the following features:
the clutch has an axially stationary and an axially movable half;
the halves of the clutch carry clutch teeth mating with each other;
the flanks of the clutch teeth are inclined making an angle of deflection in an axial direction.
A clutch of this kind should be capable, even in the presence of maximum torque, to keep itself reliably engaged with a small retaining force; with a small releasing force, even in the presence of torque to disengage quickly and reliably; and in the presence of small torque and low relative speed to engage quickly and reliably.
The first requirement necessitates a small or even negative deflection angle. Then, only a small or even no retaining force is necessary on the movable half in order to keep the clutch engaged, even in the presence of maximum torque.
The other two requirements lead to a large deflection angle. When the deflection angle is large enough, each torque quickly and reliably disengages the clutch automatically due to the axial deflection force of the clutch teeth and a releasing force on the movable half is unnecessary. With a large deflection angle, the clutch can be easily engaged in the presence of a small torque and small relative speed since the tooth gaps of the clutch teeth are so wide that the tooth heads always quickly and reliably find their tooth gaps.
If the deflection angle is going to be enlarged beyond the hitherto customary limit, an axial bearing is required to directly transmit the axial retaining force from an external actuation member to the movable half. The bearing poses difficulties either by its wear or by its size, since such a large deflection angle in the presence of maximum torque produces a very great deflection force causing wear in the bearing or requiring a very large bearing.
The above also applies to the already known claw coupling of DE-OS 19 30 668.
There exists a known clutch (German Patent 945 201) in which a sliding sleeve, with balls as intermediate members, pushes a movable half against a stationary half and in which one cylindrical locking surface holds the intermediate members firmly in a locking position between a bearing surface of the movable half and an axially stationary retaining face. However, the clutch is a friction multi-disc clutch in which no deflection angle can be changed and thus no compromise sought between light retention and light release of the clutch, but in which a great axial retaining force is always needed on the movable half in order to keep the clutch engaged and in which the release of the clutch always requires only a small or absolutely no releasing force.
The invention is based on the problem of providing a clutch of the kind described above which meets all three conditions mentioned.
The present invention solves the problem with intermediate members located axially between a bearing surface of the movable half and an axially stationary retaining surface. With this construction, even in the case of maximum deflection angle and maximum torque, only a small external retaining force and a small releasing force on the sliding sleeve is required. The torque automatically disengages the clutch quickly and reliably upon application of a small releasing force.